This invention is in the field of devices implanted within a human body for the purpose of automatically detecting the onset of myocardial infarction, warning the patient that a myocardial infarction is occurring and promptly releasing medication into the bloodstream for the purpose of dissolving obstructive thrombus in a coronary artery thus ameliorating damage to the myocardial tissue which would otherwise occur. The invention also includes the capability for treating ischemic stroke.
Heart disease is the leading cause of death in the United States. The most prevalent fatal manifestation of coronary heart disease is myocardial infarction which is caused primarily by a thrombus that obstructs blood flow in one or more coronary arteries. The medical treatment of myocardial infarction involves intravenous delivery of a thrombolytic medication such as tissue plasminogen activator (tPA) to help dissolve the thrombus in a coronary artery. The sooner thrombolytic medication is placed into the patient""s bloodstream after the occurrence of a myocardial infarction, the sooner an obstructive thrombus will be dissolved and some perfusion of the myocardium can occur. The extent of permanent damage to the myocardium is highly dependent upon the length of time that occurs prior to restoration of blood flow to the heart muscle. However, at this time no implantable system exists that provides for early and automatic detection of myocardial infarction. Furthermore, no system exists that would provide automatic and immediate release of an anti-thrombogenic or thombolytic agent into the bloodstream to dissolve an obstructive blood clot at the earliest possible time and prevent the recurrence of a blood clot.
One of the most debilitating diseases to which human beings are subjected is thrombotic stroke that is caused by a blood clot blocking a cerebral artery. There are approximately 500,000 such strokes in the USA each year with a 30 day survival rate of less than 80%. The lifetime cost for treatment of each of these patients exceeds $90,000. Therefore, any treatment modality that could decrease brain damage from thrombotic stroke would be highly advantageous to the population of the USA and the rest of the world both from a health point of view and from a cost saving prospective.
Approximately 40% of stroke survivors will suffer a cardiovascular death. Furthermore, in the first few months after a myocardial infarction there is a 5% probability of stroke. However, there is no extant system that includes an implanted medication release device that can treat either or both a stroke or a myocardial infarction.
One embodiment of the present invention is a completely implantable system that can detect the occurrence of a myocardial infarction, i.e., a heart attack, within less than a minute after it begins and then automatically inject a thrombolytic and/or anti-thrombogenic agent into the bloodstream to promptly dissolve the thrombus that caused the myocardial infarction and to prevent the formation of additional thrombi.
It is well known that a myocardial infarction can be detected from a patient""s electrocardiogram by noting an ST segment deviation (e.g., voltage increase) as compared to the voltage of the patient""s TP or PQ segments. Such an ST segment deviation can be even more clearly discerned with electrodes implanted within the body (especially within or in close proximity to the heart) as compared with detecting the deviated ST segment from chest or limb mounted electrodes. The signal from the heart using implanted electrodes is called an xe2x80x9celectrogramxe2x80x9d. By means of an electrogram, early detection of a thrombus causing myocardial ischemia is clearly feasible. Furthermore, the patient""s level of pO2 and/or his heart rate (each of which can be determined from an implanted part of the system) can also used either by itself for pO2 or in conjunction with ST segment deviation (for pO2 and heart rate) to verify the presence of a myocardial infarction as opposed to some other cause of coronary ischemia.
Upon detection of a myocardial infarction, an ST segment deviation electronic detection circuit within the implanted device can produce an output signal that can cause a thrombolytic and/or anti-thrombogenic agent contained within an implanted reservoir to immediately and automatically release medication into the patient""s bloodstream. Thus, the thrombolytic agent is placed into the bloodstream for dissolving an obstructive thrombus at the earliest possible time. Therefore, both mortality and morbidity can be dramatically reduced. In fact, it is possible that such a system could significantly decrease the initial risk of a fatal ventricular arrhythmia as well as myocardial tissue necrosis that often progresses to congestive heart failure.
It is envisioned that additional embodiments of the present invention can include a patient warning system that informs the patient by either an audio alarm or by an electrical tickle within his body that a myocardial infarction has been detected and that a thrombolytic agent has been released. At the occurrence of such an alarm, the patient can be instructed to seek immediate medical care.
An additional embodiment of the present invention is for the implanted system to send a radio message to a receiver within the patient""s home that automatically dials an emergency rescue team to take the patient to a hospital for continuing treatment of his myocardial infarction.
Still another embodiment of the invention includes either an implanted defibrillator or heart pacemaker that would be used in conjunction with the system for automatic release of a thrombolytic agent.
Although the previous discussion addresses only the situation involving a myocardial infarction, it would be highly advantageous to have an implanted system that can treat either or both a myocardial infarction or a thrombotic stroke. The implanted portion of such a system is defined herein as a cardiosaver-strokesaver device. The entire system including portions that are not implanted within the patient is defined herein as a cardiosaver-strokesaver system. It is also envisioned that a cardiosaver-strokesaver device could be combined with a conventional implantable defibrillator and/or pacemaker. The combined capability of the cardiosaver-strokesaver system would be capable of automatically introducing an anti-thrombogenic or thrombolytic drug into the patient""s vascular system if a myocardial infarction is detected or the drug could be administered by the patient or by someone close to the patient if an early symptom of a stroke is detected. These early symptoms of a stroke that could be used to trigger the release of medication are: (1) sudden weakness or numbness of the face, arm or leg on one side of the body: (2) sudden dimness or loss of vision, especially in one eye; (3) loss of speech or trouble talking or understanding speech; (4) sudden and severe headache with no apparent cause; and (5) an unexplained dizziness, unsteadiness or sudden falls. The patient and/or a person living with or taking care of the patient (collectively the patient caregiver) would be taught all of these early signs of a stroke. At the onset of any such early sign, the patient or the patient caregiver would use a patient operated initiator to trigger the release of a medication from the implanted cardiosaver-strokesaver device to restore patentcy to the cerebral artery that has a thrombotic blockage. Thus, the cardiosaver-strokesaver device would have the capability to automatically release medication to treat a myocardial infarction and would also have the capability to release medication by action of the patient operated initiator to prevent brain damage in the event of a stroke.
Patient selection for such a cardiosaver-strokesaver system is of great importance. It is anticipated the cardiosaver-strokesaver system could be part of any pacemaker and/or automatic defibrillator that is implanted into any human subject that requires such a device. Furthermore, the cardiosaver-strokesaver system would be advantageously placed in any human subject who has one or more of the following conditions: (1) atherosclerosis; (2) hypercholesterolemia; (3) high blood pressure: (4) a family history of myocardial infarction; (5) a family history of stroke; (6) transient ischemic attacks (TIA""s); (7) a prior myocardial infarction; (8) a prior stroke; (9) diabetes; or (10) untreatable atrial defibrillation.
Thus it is an object of this invention to have an implanted system that releases a thrombolytic and/or anti-thrombogenic agent into the bloodstream of a human body upon detection of either a myocardial infarction or a stroke.
Another object of this invention is to automatically inform the patient that a myocardial infarction has occurred by means of an alarm such as a subcutaneous electrical tickle or audio signal.
Still another object of this invention is to utilize the automatic myocardial infarction detection and medication release system (the cardiosaver portion) and the manually activated system to release medication to treat the early symptoms of a stroke (the strokesaver portion) in conjunction with an implantable defibrillator and/or pacemaker.
Still another object of this invention is to have an implanted defibrillator or pacemaker that includes sensors (such as electrodes) to sense a myocardial infarction and to trigger an internal alarm and an externally located alarm to inform the patient that he has the indication of a myocardial infarction. This system could provide specific instructions for self-administration of additional medications.
Still another object of this invention is to have a combined cardiosaver-strokesaver system that sends a radio signal to a receiving system located in close proximity to the patient which then makes a telephone call to a rescue service that sends an ambulance to bring the patient to a hospital.
Still another object of this invention is to have an implantable myocardial infarction detection system that sends a radio signal to a receiving system in the patient""s home that informs the patient that he may be undergoing a myocardial infarction and that an ambulance has been called to bring him to a hospital and that he should take certain actions such as taking an aspirin tablet.
Still another object of the invention is to use more than one physiological parameter (such as any combination of ST segment deviation, pO2, heart rate, etc.) to verify the occurrence of a myocardial infarction.
Still another object of this invention is to provide a patient with a patient operated initiator which he could use to initiate the release of one or more medications that have been placed into the implanted portion of the cardiosaver-strokesaver system.
Still another object of this invention is to provide a means for informing the patient that he is having a myocardial infarction when he might otherwise ignore some particular symptom or he may not have perceived any symptom.
Still another object of this invention is to have an implantable system for the detection of a myocardial infarction that also has the capability for storing electrograms.
These and other objects and advantages of this invention will become obvious to a person of ordinary skill in this art upon reading of the detailed description of this invention including the associated drawings as presented herein.